A Broad-Spectrum Antagonistic Bacillus Velezensis Strain HY17 as a Potential Biocontrol Agent Aagainst Major Maize Fungal Diseases.

Maize fungal diseases seriously threaten crop productivity and grain quality, highlighting the need for effective and sustainable biocontrol agents. In this study, an antagonistic bacterium, HY17, was isolated from maize rhizosphere soil and identified as Bacillus velezensis based on morphological characterization and phylogenomic analysis. HY17 exhibited broad-spectrum antifungal activity against several major maize fungal pathogens. Its cell-free fermentation supernatant showed clear concentration-dependent inhibition of fungal growth, indicating that extracellular metabolites play an important role in their antagonistic activity. HY17 also displayed broad growth adaptability under different culture media, temperature, and pH conditions. Whole-genome analysis revealed that HY17 contains a chromosome of 3,931,127 bp and multiple biosynthetic gene clusters associated with antimicrobial secondary metabolites. Crude lipopeptide extracts from HY17 further exhibited concentration-dependent antifungal activity. PCR assays detected representative antimicrobial biosynthetic genes, including bacA, bmyB, ituC, fenD, and srfAA, and LC-MS analysis revealed characteristic ion peaks putatively assigned to iturin-family lipopeptides and a fengycin-family component. Collectively, these results indicate that B. velezensis HY17 is a promising biocontrol candidate for maize fungal diseases, with lipopeptide-related metabolites likely contributing substantially to its broad-spectrum antifungal activity.